The “new wood”: Upcycled coffee grounds could serve as alternative bioplastics source

29 Apr 2020 --- Used coffee grounds can be upcycled to serve as a new non-wood source “in large amounts worldwide,” according to new research from Yokohama National University, Japan. The research team found that the amount of cellulose contained in coffee grounds per gram of dry weight is much lower than that of wood. Predicting that these coffee grounds could contribute to developing sustainable green chemistry in the form of bioplastics, solid collaboration between academia, government and industry must first be established.

The study found that 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation of spent coffee grounds (SCGs) containing 10 percent cellulose in dry weight successfully produced the cellulose nanofibers derived from this biomass. Observed by scanning electron microscopy, the researchers identified the TEMPO-oxidized cellulose nanofibers (TOCNFs) as 20 to 35 nm wide. 

“We believe that by using TEMPO-oxidation, we can get the TOCNFs from the used coffee grounds. We must improve the quality of nano-scale structural data to prove the isolation of TOCNF,” co-author Izuru Kawamura, Associate Professor at the Yokohama National University Graduate School of Engineering, tells PackagingInsights.

To investigate the interaction of these TOCNFs with a polymer, the research team prepared an SCG-derived TOCNF composite film with poly(vinyl alcohol) as a water-soluble polymer. “We found the TOCNFs were successfully integrated into the polymer. The outcome of this study indicated that SCGs could be used as well as wood as an alternative source for producing TOCNFs,” the study reads.

“We have gathered very nice structural data of the TOCNF. The preparation of the composite films with soluble polymer has also been developed on the other research of wood-derived cellulose nanofibers. Consequently, we can easily prepare it, but we are excited about the formation of the film containing SCGs-derived TOCN,” Kawamura affirms.

The fact that coffee is consumed all over the world and there are a certain amount of coffee grounds discarded every year is both concerning and encouraging in the eyes of Kawamura. Moreover, fundamental implementation hurdles still exist. For one, the collection of SCGs remains “a big problem” and further research in the field of upcycling is “a secret,” he says.

“If we could make effective use of the SCGs, we could not only use them as bioplastics but also improve fuel economy by making light and robust cars,” Kawamura adds.

Promising moves toward a circular food system have already witnessed inter-sectoral collaboration, exemplified by McDonald’s partnership with Ford Motor Company last year. The two companies experimented with creating new vehicle parts using disposed coffee grounds. 

Also, German company Kaffeeform has created a composite material made from 40 percent coffee grounds. The material can be used to construct coffee cups.

By Anni Schleicher

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